An aerial team spotted Udall’s body on its side, in open, rolling terrain Wednesday afternoon, Sublette County sheriff’s officials said. The body was taken to Pinedale.

The office of Mark Udall, a Democrat of Colorado, released a statement from the family saying that although an autopsy is forthcoming, it appears his brother died of natural causes.

‘‘Randy left this earth doing what he loved most: hiking in his most favorite mountain range,’’ the family said.

He had indicated on a sign-in sheet at the trailhead that he planned to head for the scenic Titcomb Basin.

Randy Udall was an environmentalist and energy efficiency-advocate whose family has been active in politics. Senator Tom Udall of New Mexico is a cousin. His uncle, Stewart Udall, was interior secretary in the 1960s.